Process for recovering glycerin



March 26, 1940. B. CLAYTON 2,195,

A PROCESS FOR RECOVERING GLYCERIN Filed Nov. 3, 1957 2 Sheets-Sheet 1 March 26, 1940. B. CLAYTON IROCESS FOR RECOVERING GLYCERIN Filed Nov. 3, 1937 2 Sheets-Sheet 2 b hm 9% m, vmzbwm Patented Mar. 26, 1940 PATENT OFFICE PROCESS FOR RECOVERING GLYCERIN Benjamin Clayton, Houston, Tex., assignor to Refining, Inc., Reno, Nev., a corporation of Nevada Application November 3, 1937, Serial No. 172,644

4 Claims.

This invention relates to a process for recovering glycerin and more particularly to a process for recovering glycerin from admixture with soap.

In the production of soap from fats and oils containing glycerin in combination, relatively large proportions of glycerin are produced and this glycerin constitutes a valuable by-product. The conventional process of separating and recovering the glycerin from the soap mixtures is by adding salts such as sodium chloride to the mixture to cause the same to separate into layers, one consisting essentially of soap and the other including water, glycerin and added salt. The 5 two layers are separated by decantation and by this means glycerin liquor containing large amounts of salt and water is produced. The

tillation to produce a high glycerin content.

During this stage the presence of large amounts of salts which are poor heat conductors results 5 both in large expenditures of heat and in superheating and requires the application of high temperatures'for extended periods of time, all of which causes a decomposition of glycerin into products like acrolein, trimethylene glycol and 0 other decomposition products.

In accordance with the present invention the soap mixture is heated out of contact with the atmosphere to a temperature sufliciently high to cause the glycerin to be evaporated under vacuum 5 conditions and the glycerin is thereby directly separated from the soap in relatively pure form without the addition of any salts or other materials for causing separation of the glycerin. The soap mixture treated in accordance with the 0 present invention may be produced by the conventional batch processes but may be advantageously produced in a continuous process such as disclosed in the copending application, Serial No. 119,168, filed January 5, 1937. Such continuous 5 processes of making soap mixtures involve the continuous mixing of oil or fat and alkali solutions at elevated temperatures and out of contact with the atmosphere to produce soap and glycerin. Such a soap mixture or one produced by the conventional batch process may be heated to a glycerin vaporizing temperature and delivered into a vacuum chamber wherein the glycerin is volatilized and removed in vapor form from the soap. The escape of glycerin from the soap is a function of -temperature,- time and amount of vacuum. It is generally necessary to heat the soap to a temperature at which it is liquid after the glycerin has been removed in order to effect substantial complete volatilization of the glycerin. Sumcient time must be provided for the W It is, therefore, an object of the invention to, i

provide a process of separating glycerin from soap under high temperature conditions in which the glycerin is rapidly separated from the soap before decomposition of the soap or glycerin is produced. v

Another object of the invention is to produce substantially pure glycerin directly from mixtures containing soap and glycerin. 1

In order to cause rapid separation of glycerin from the soap, it has been found advantageous to spread the heated mixture in thin films upon surfaces in a vacuum chamber. Preferably these surfaces are heated so as to maintain the temperature of the heated mixture.

It is, therefore, another object of the invention to provide a process of separating glycerin from soap by spreading a heated soap and glycerin mixture in thin films upon surfaces in a vacuum zone.

Another object of the invention is to separate glycerin from heated soap and glycerin mixtures in a vacuum chamber by spreading the same in thin films upon heated surfaces.

This operation is preferably accomplished by directing the heated mixture against heated walls of a vacuum chamber by means of a nozzle or other opening. The particles as they strike the wall form a film of soap which slides down the walls. The film is an eflicient means of exposing a large portion of the soap mixture from which the soap can be released. By controlling the distance through which the soap mixture travels down the walls of the chamber sufllcient time can be provided for substantially complete separation of glycerin without substantial damage to the soap or glycerin.

This method of' evaporating glycerin from a soap mixture produces entirely different results than merely spraying the mixture of soap and glycerin into the chamber. While the film travels down the sides of the chamber only its clean sur-' face isin contact with the kettle atmosphere whereas the particles of soap formed by spraying have their clean surfaces exposed to the kettle atmosphere for only a comparatively short time before they fall to the bottom of the chamber. In spraying operations, mounds or heaps of soap build up on the bottom of the chamber and this interferes with the proper volatilization of the glycerin from the soap. A much longer time must be provided to reach the desired degree of volatilization of the glycerin and the soap must be exposed to the chamber temperatures for longer times. Also small soap particles formed by spraying are blown over or carried with the vapors and the soap in the bottom of the chamber does not release volatiles smoothly but sudden explosive upheavals occur in the soap mass resulting in the blowing up of soap particles which are entrained in the vapors removed from the chamber.

By directing the soap against the walls of the chamber a downward flowing film of soap is produced which looses volatiles as it travels down I the sides of the chamber. There is no building up of soap particles or superposed soap films resulting in explosive liberation of vapors. The carrying over of soap particles with the vapors is thereby greatly minimized and the volatilization of glycerin takes place smoothly and rapidly.

A particularly effective way of discharging the mixture of glycerin soap against the wall of the vacuum chamber is to use revolving nozzles. The revolving nozzle makes efficient use of the kettle as the entire circumference of the surface of the walls is coated with a thin downwardly flowing film of soap from which the glycerin is rapidly and smoothly released. Stationary discharge nozzles which direct the mixture against the walls of the chamber are also contemplated by the present invention, although only that surface of the kettle within the fan-like spray is utilized in the volatilization of glycerin from the soap.

It is, therefore, an object of the invention to provide a process and apparatus in which the entire circumference of the walls of a vacuum chamber is employed for glycerin volatilization.

Other advantages and objects of the invention will appear in the following description of preferred embodiments of invention described in connection with the attached drawings, of which:

Figure 1 is a schematic view of a complete apparatus for recovering substantially pure glycerin from soap,

Figure 2 is a fragmentary view in section of an evaporating chamber showing one type of revolving nozzle,

Figure 3 is a horizontal section taken on the line 3-3 of Figure 2,

Figure 4 is a fragmentary sectional view of the bearing arrangement of the nozzle of Figures 2 and 3,

Figure 5isaviewsimilartoFigure2 showinga modified form of revolving nozzle; and

Figure 6 is a horizontal cross-section taken on the line 6-6 of Figure 5.

Referring more particularly to the drawings, in Figure 1, l0 indicates a source of supply of soap mixture which may be a conventional soap kettle provided with an agitator ll driven from any suitable source of power through a pulley l2.

As indicated before, any other suitable source of soap mixture may be employed, 'for example, a continuous saponification process disclomd in application Serial No. 119,168 referred'to above. The soap mixture may be pumped by a high pressure pump I! through a heating device shown as a coil I4 and into an evaporating chamber 15. The temperature of the mixture is raised in the heating coil II by any suitable means such as a burner It for gaseous or liquid fuel, to a temperature sufficiently high to cause glycerin to be evaporated in the evaporating chamber l5. While only one coil I4 is shown, two or more such coils in which the mixture is brought to successively highertemperatures in series may sometimes be desirable along with additional pumps between the coils to force the mixture therethrough. The temperature reached in coil or coils I 4 will depend upon the type of soap being processed but will usually fall between temperatures of 450 and 620 F. These temperatures are usually above the decomposition point of the materials from which the soap was made and care must be taken that substantially complete saponification is obtained before subjecting the mixture to such high temperatures. In Figure 1 stationary nozzles I! are shown and the soap mixture is discharged against the wall l8 of the evaporating chamber [5. The soap mixture fiows down the wall IS in a thin film such that the glycerin vapors are rapidly and substantially completely liberated. Relatively high superatmospheric pressures are usually employed in the coil H to prevent too great vaporization therein. Thus pressures ranging from 50 to 1,000 pounds imposed by the pump I3 and maintained by restricted orifices in the nozzles H, by a valve [9 in the pipe leading from the coil II to the evaporating chamber lb or by making the pipe of coil ll sufficiently small, may be employed in the coil ll depending upon the amount of vaporization desired therein. By employing pressures in the upper portion of the range above given, the mixture may be maintained substantially all in liquid phase in the coil ll but in general it has been found preferable to provide at least partial vaporization of glycerin in the coil 14 in order to increase theamount of heat which may be imparted to the mixture therein. As any vaporization of glycerin in the evapo rating chamber I5 tends to cool the film of mixture upon the walls I8, it is generally necessary to supply additional heat to the mixture in the evaporating chamber l5. This can be conveniently done by enclosing the evaporating chamber within a heating jacket through which any desired heating medium such as steam or heated mineral oil may be circulated by means of the pipes 2| and 22. Additional heat for vaporization can thereby be supplied directly to the film of mixture upon the wall I! and the soap may be maintained in liquid form after water and glycerin vapors have been removed therefrom so that it will flow downwardly into the lower portion of the evaporating chamber I. Also additional heat may be supplied by introducing steam, preferably superheated to a temperature at least as high as that of the mixture leaving the coil l4, into the vacuum chamber, for example, by the pipe 22'.

In order to promptly remove the soap from the evaporating chamber and to cool the same, a screw conveyor 23 provided with a cooling jacket II can be conveniently employed. Such a device is effective to continuously discharge the substantially anhydrous soap from the evaporating chamber without breaking the vacuum and also to cool the soap below a temperature at which it would be damaged by contact with the air before contacting the soap with the air.

The housing 25 of the conveyor 23 forms a part of the evaporating chamber l5 and the soap is delivered through a restricted passage formed by enlarging the end portion 2. of the conveyor so as h plug the conveyor housing against entrance of air. A valve 21 may be provided in the discharge end of the conveyor housing so that the vacuum may be maintained during starting and stopping of the apparatus when no soap is present in the conveyor housing 2!.

The vapors are withdrawn from the evaporating chamber through a pipe 28 and may be delivered to an entrainment separator 29. It will be noted that discharging the mixture against the walls of the chamber l5 and causing the same to flow downwardly along the walls, provides a substantially unimpeded path for the vapors upwardly through the evaporating chamber Ii. The vapors are thus not required to pass through a spray of material and entrainment is largely prevented. Entrainment separator 28 has been illustrated as including a helical baiiie 30 formed between the casing 3| of the entrainment separator and an inner baiiie 32 so that the vapors passing through v the separator are forced to follow a helical path the wall lief. the evapcratingchamber may carry and then make an abrupt turn upwardly through the banie 32 to the vapor withdrawal pipe 33. Thus entrained liquids or solids are thrown out of the vapors and are conducted back to the evaporating chamber through the pipe 34.

One or more condensers 35 provided with receivers 38 are provided for condensing the glycerin water vapors withdrawn from the vacuum chamber I! either in a single condenser or in any desired fractions in several condensers. A vacuum is maintained in the receivers, condensers and evaporating chamber II by means of a vacuum pump 31 connected to the last receiver 30. It is desirable to maintain as high a vacuum as commercially practicable in'the evaporating and condensing system. Thus, vacuums ranging from 26 to 29 inches of mercury have been successfully employed. Condensate may be withdrawn from the receivers 36 through pipes 38 by any suitable means, for example, pumps not shown.

The structure shown in Figures 2, 3 and 4 provides rotating nozzles 39 by whic the heated soap mixture may be distributed around the periphery of the wall it of the evaporating chamber. The soap mixture may be delivered into the chamber with considerable velocity and by radially inclining the nozzles 39 as shown in Figure 3 and pivotally connecting,the nozzles at 40 with the pipe 4] delivering the mixture into the chamber, the nozzles can be caused to revolve. A suitable rotary connection for the nozzle is shown in Figure 5 and may include a stationary element 42 to which the pipe 4| is connected by means of a threaded member 43. A pipe 44 supporting :nomles ll is 'rotatively secured to the member 4! by an antifriction bearing including bearings ll, a bearing race 48 secured to the stationary member 42, and a bearing race 41 secured to the rotary pipe 44. A nipple ll is secured to the stationary member 42 and extends downwardly within the rotary pipe 44 and a flange 48 may be secured to the rotary pipe 4! for preventing entrance of extraneous.

materials into the bearing races 48 and 41. By this structure .the nozzles I! will continuously revolve in the same manner as a reaction turbine.

.be accurately controlled. Thus, a rotating member 50 extending through a packing gland Si in rotating nozzles 52. The shaft II and nonles 52 may be rotated by a bevel gear "secured to the the pipe II which delivers the heated material to the evaporating chamber in the shaft I through any suitable rotary connection II, the heated mixture may be delivered continuously around the periphery of the wall It of the evaporating chamber at any desired speed depending upon the speed of the pinion ll. If desired, the shaft ill may continue downwardly and drive a scraper (not shown) in the lower portion of the evaporating chamber in order to insure that the soap is continuously delivered into the conveyor housing 25. Examples of the products resulting from the present process are given in the following table:

Table I Percent istty Amount Amount of Percent oi Run soap total glycglycerin in airz ig gg proerin concondenglycerm com duced densates sates demm Pounds Percent Percent The amount of total glycerin condensates represents all of the condensate collected in the condenser system and it will be noted that the amount of these total condensates is always much less than the amount of soap produced, in most cases being only slightly more than 50% of that amount. This is contrasted with the conventional method of salting out glycerin, in which the glycerin waters or spent lyes range from an amount approximately equal to the soap produced to three times as much or more. This means that much less water must be evaporated in the a present process to produce a concentrated crude Table 1! Combined condensates of 8 nt lye I present process iquors Percent]! cerin 11-18% 3 10%. Amounto salt None 1-167. or anic impurities" From lea than 0.09%-0.40%. More than 1%.

As an example of the composition of the various condensates which can be obtained from a condenser system employing four condensers, the

following table relating to Run #1, of Table I -is.

given:

Table m P d Percent Peres: lstt oun s o y ms nfl condensate in condencludlng'sosp sate in condensate 5. 25 81. s 2. 4s 24. 0 I. 5 0. 81 357. 0 9. 0 0. 2s 16. 5 1. 0 0. 0

It will benoted that a large percentage. of the impurities was collected in the first condenser which was nearest the evaporating chamber and that the other condensates are relatively pure.

The bulk of the condensate was condensed in condenser #3 which contains 9% glycerin and only 0.28% of impurities.

When the glycerin water from the conventional glycerin salting out processes are chemically treated to remove impurities and are evaporated at the expense of large amounts of heat to concentrate the glycerin and crystallize out large amounts of salts, large amounts of impurities remain therein. The composition of three crude glycerins obtained from such processes are given by the following table:

Table IV I II III Percent Percent Percent Percent glycerol c. 82. 54 79.18 56. 47 Non-volatile organic matter l. 16 3. 45 14. 55 Ash 8. 28 9. 68 19. 66

A comparison of such crude glycerins from such conventional processes and the total condensate from the present process evaporated to approximately 80% glycerin is given in the following table:

Table V Evapo- Crude glycerin of present rated process crude glycerin Percent Amount oi salt None 5-15 Non-volatile organic 0.55.0% 1. 0-15 matter. Ash From less than 0.l0.8% 8. 0-20; 0

In the above table, the amount of ash tabulated for the present process is from the nonvolatileorganic matter, chiefly soap, as there are f i result in thermal decomposition thereof to produce products such as acrolein, trim'ethylene, glycol, etc., which products are present in the condensed glycerin and are diflicult to remove therefrom.

Also the present process provides for an almost complete separationofthe glycerin from the soap. Soap containing much less than 1% glycerin has been consistently produced by the present process; The amount of glycerin retained in the soap, if a glycerin carrying soap is desired, may, however, be easily controlled by varying the temperature atwhich the soap mixture is introduced into the evaporating chamber, the temperature or vacuum maintained therein,

or the length of time the soap remains in the.

evaporating chamber of any combination of these conditions.

While I have described the preferred embodi-- ments of the invention, it is understood that the.

vaporize said glycerin and minimize entrainment.

of soap in the resulting vapors, withdrawing and condensing said vapors and immediately withdrawing the glycerin free soap, before decomposition thereto, without substantially diminishing the said vacuum conditions.

2. The process of recovering glycerin from mixtures containing soap, glycerin and water, which comprises, discharging a stream of said mixture against the wall of a chamber in which a vacuum is maintained, applying sufficient heat through the wall of said chamber to maintain said mixture in liquid condition and cause the same to flow as a film down said wall and substantially all of said glycerin and water vapors to be vaporized therefrom without causing solidification of said film, removing the resulting vapors from said chamber condensing the same to produce a substantially pure mixture of water and glycerin and immediately withdrawing the glycerin free soap, before decomposition thereto, without substantially diminishing the said vacuum conditions.

3. A process of producing soap and recovering vaporizable materials resulting from the saponification of the saponifiable and saponifying materials which comprises the steps of reacting a saponifiable materiallwith a saponifying-reagent to effect substantial saponification, thereafter passing the resultant saponified mixture including soap and said vaporizable materials through a heating zone, supplying suflicient heat to said materials in said zone to cause substantially com-, plete vaporization of said vaporizable materials when said mixture is introduced into a vapor separating chamber, introducing the mixture as a film along the surface of said chamber, maintaining a temperature above the melting point of the soap in anhydrous form so as to vaporize said vaporizable materials and water from the film of the mixture whereby to minimize entrainment of soap in the resulting vapors, withdrawing and condensing said vapors at a rate sufficient to maintain a vacuum in said chamber and withdrawing the soap from the chamber without substantially impairing the vacuum therein maintained. I

' 4. The process of producing soap and recovering glycerin comprising the steps of continuously saponifying a mixture of saponifiable and saponifying inaterials, continuously flowing a film of said mixture downwardly against the wall of an evaporating chamber, maintaining the film of soap heated to an extent sumcient to vaporize substantially all of the glycerin contained in said mixture as the film gravitates downwardly against the wall of said chamber, continuously withdrawing the glycerin vapors at a rate suflicient to maintain a vacuum in said chamber and continuously withdrawing the resultant glycerin free soap from said chamber without substantially im- BENJAMIN CLAYTON. 

